[imp] Attachment download - size issue?

[Greg R]

On attempting to download a 4390 KB attachment PHP throws the following error:

PHP Fatal error:  Allowed memory size of 16777216 bytes exhausted
(tried to allocate 5993473 bytes) in
/home/www/horde/imp/lib/MIME/Contents.php on line 173

I don't know where it is finding the 16MB memory size limit because I
have increased all size limits in php.ini to the below values as
reflected by phpinfo():

Apache/1.3.36
PHP Version 5.1.4
PHP compiled with --enable-memory-limit
post_max_size	32M
upload_max_filesize	8M
memory_limit	96M

Thanks in advance